I'm very sure Tada shihan's solo drills are for 'something' that can't be earned during daily waza practices. If not, there is no reason to do that, isn't it? I guess the 'something' is meant to build up 'something' then. Similary some other aikikai teachers also have it but such drills aren't in aikikai curriculum. Apparently the teachers are doing something else besides aikido and it's not like 'doing 2 separate things at the same time' However, if you ask the teachers, 'what's this?' or 'how do you do that?' Then probably 99% they will say, 'do this everyday' Please do some solo exercises before joining Yamshima shihan's seminar. You feel something different.